Stem Rust Research Articles

Changes in RNase activities and in expression of two RNase genes in powdery mildew infected barley, wheat and Brachypodium distachyon leaves

AbstractChanges in RNase activities were investigated in extracts from barley near isogenic lines without or with various powdery mildew resistance genes and were compared to changes in wheat and Brachypodium distachyon leaves after powdery mildew infections. In barley, the compatible interaction with powdery mildew induced the highest increase in RNase activity as measured spectrophotometrically. The incompatible interaction that accompanied with hypersensitive reaction in Mla leaves gave less increase, whereas incompatible interactions in Mlg and mlo barley leaves without visible symptoms gave the least increase of RNase activity. In wheat, the largest RNase activity was found in leaves infected with the compatible wheat powdery mildew or wheat stem and leaf rusts. RNase activity in B. distachyon was higher than that in healthy wheat and especially barley leaves. The electrophoretic RNase enzyme activity patterns were different in barley, wheat and B. distachyon plants, but showed similar activities as determined spectrophotometrically. Barley genes encoding endonuclease 2 and ribonuclease 3-like protein X3 showed the highest expression in the compatible barley - barley powdery mildew interaction as measured by RT-qPCR. This correlated with RNase activities in leaf extracts suggesting that RNases in barley and wheat may act as susceptibility factors of powdery mildew and rust diseases.

Multi-environments Evaluation of Zn and Fe Enhanced Bread Wheat Genotypes in Optimum Areas of Ethiopia

A multi-location experiment was conducted during June, 2020–October, 2021 under rainfed condition at Kulumsa, Asasa, Adet, Holeta, and Sinana Research centers, Ethiopia to evaluate the genotype-by-environment interaction effect and grain yield stability of Zn and Fe enhanced bread wheat genotypes grown. The treatments constituted 21 advanced genotypes and two standard checks were evaluated in an alpha lattice design replicated three times and data analysis was carried using R software. The results showed that genotypes and genotype x environmental interaction had a significant (p<0.001) effect on days to 50% heading, days to 90% maturity, plant height, grain yield, and 1000 kernel weight. The bread wheat lines BW172862, EBW193416, BW172864, and EBW193414 were high-yielding across most test environments, whereas genotype EBW192455 and Hidasse were low-yielding ones. From stability analysis genotypes BW172862, and EBW193416 were identified to be the most adapted bread wheat genotypes. “BW172862 produced 24.43% and 86.38% yield advantage over the standard check (Lemu) and local check (Hidasse), respectively. The second candidate genotype EBW193416 also produced 23.58% and 85.1% yield advantage over the standard check (Lemu) and local check (Hidasse), respectively. EBW193416 and BW172862 have also exhibited lower Yellow and Stem rust severity compared to others across the test environments. Thus, BW172862 and EBW193416 were selected as best parent to recycle for bread wheat population improvement in 2023 for medium agro-ecology of Ethiopia.

In silico determination of potential miRNAs encoded in wheat genome that target AvrSr35 in Puccinia graminis f. sp. tritici

Wheat (Triticum aestivum L.) belonging to Poaceae family is a valuable staple food all over the world. Puccinia graminis f. sp. tritici is one of the major limiting factor in wheat production, causing stem rust disease. RNA interference (RNAi) is an effective technique for plant production against abiotic stresses. One of the most investigated RNAi molecules is microRNAs (miRNAs). It is well established that miRNAs play important role for the regulation of gene expression at post-transcriptional and pos-translational level. In the present study, wheat miRNAs-stem rust interactions were investigated by in silico methods. For this purpose, reference mature wheat miRNAs were retrieved from miRBase, and the sequences of avirulence gene (AvrSr35) in Puccinia graminis f. sp. tritici were obtained from NCBI. RNAhybrid algorithm was used to predict the relationships between miRNAs and avirulence gene targets. Moreover, a phylogenetic tree was constructed by using miRNAs via MEGA X. We determined that AvrSr35 gene was targeted by a total of 12 miRNAs including tae-miR9657a-3p, tae-miR9671-5p, tae-miR1122c-3p, tae-miR1130b-3p, tae-miR9678-3p, tae-miR9781, tae-miR9666b-3p, tae-miR531, tae-miR9773, tae-miR9778, tae-miR9677b and tae-miR10516. All miRNAs were separated into three major groups. All miRNAs showed close relationship. The first main group consisted of only tae-miR9778. Obtaining findings are expected to contribute roles of miRNAs in the interaction between disease-related miRNAs in plants and pathogens.

Evaluation of genetic variation and host resistance to wheat stem rust pathogen (Puccinia graminis f. sp. tritici) in bread wheat (Triticum aestivum L.) varieties grown in Türkiye.

Wheat stem rust, which is caused by Puccinia graminis f. sp. tritici (Pgt), is a highly destructive disease that affects wheat crops on a global scale. In this study, the reactions of 150 bread wheat varieties were evaluated for natural Pgt infection at the adult-plant stage in the 2019-2020 and 2020-2021 growing seasons, and they were analyzed using specific molecular markers to detect stem rust resistance genes (Sr22, Sr24, Sr25, Sr26, Sr31, Sr38, Sr50, and Sr57). Based on phenotypic data, the majority of the varieties (62%) were resistant or moderately resistant to natural Pgt infection. According to molecular results, it was identified that Sr57 was present in 103 varieties, Sr50 in nine varieties, Sr25 in six varieties, and Sr22, Sr31, and Sr38 in one variety each. Additionally, their combinations Sr25 + Sr50, Sr31 + Sr57, Sr38 + Sr50, and Sr38 + Sr57 were detected in these varieties. On the other hand, Sr24 and Sr26 were not identified. In addition, many varieties had low stem rust scores, including a large minority that lacked Sr57. These varieties must have useful resistance to stem rust and could be the basis for selecting greater, possibly durable resistance.

Phenotypic and molecular characterization of pleiotropic resistance to rusts and powdery mildew in spring wheat

An attempt was undertaken to comprehend how phenotypic markers, leaf tip necrosis (LTN), and pseudo black chaff (PBC), are associated with pleiotropic resistance genes in wheat (Triticum spp.). Pleiotropic resistance to stripe rust (Puccinia striiformis f. sp. tritici), leaf rust (P. triticina), stem rust (P. graminis f. sp. tritici) and powdery mildew (Blumeria graminis f. sp. tritici) was evaluated in 57 Egyptian spring wheat cultivars at seedling stage in greenhouse and at adult plant stage in field during 2021/22 and 2022/23. At seedling stage, pleiotropic resistance rated moderately resistance (MR) was observed in five cultivars, Misr-3 (all three rusts), Misr-4 (stripe rust, leaf rust, powdery mildew), Giza-168 (leaf rust, stem rust, powdery mildew), Sakha-94 and Sids-13 (leaf rust, stem rust). At adult plant stage, Misr-4 outperformed all other evaluated cultivars, exhibiting a high level of pleiotropic adult plant resistance (PAPR) against all diseases investigated. High levels of PAPR were also noticed against the three rusts in nine cultivars, Misr-3, Sakha-93, Sakha-94, Sakha-95, Giza-156, Giza-168, Giza-171, Gemmeiza-10 and Sids-13, and moderate levels against powdery mildew in Misr-3, Sakha-95, Giza-156. Four PAPR genes were characterized in cultivars based on phenotypic and molecular markers. Phenotypic markers (LTN and PBC) were observed in 23 cultivars. Molecular marker csLV34 indicated the presence of Lr34/Yr18/Sr57/Pm38/Ltn1 in six cultivars, whilst marker Xwmc44 indicated that Lr46/Yr29/Sr58/Pm39/Ltn2 was present in five cultivars. Marker Xcfd71 indicated the presence of Lr67/Yr46/Sr55/Pm46/Ltn3 in 19 cultivars. Gene Sr2/Yr30/Lr27/Pbc was identified with marker csSr2 in three cultivars. A complete association between LTN and molecular markers was recorded, while a strong association (r = 0.73) was recorded between PBC and molecular markers. Findings demonstrated the reliability of phenotypic markers in predicting pleiotropic resistance in wheat, which would facilitate marker-assisted selection in breeding programs.

Optimizing an integrated biovigilance toolbox to study the spatial distribution and dynamic changes of airborne mycobiota, with a focus on cereal rust fungi in western Canada.

In the face of evolving agricultural practices and climate change, tools towards an integrated biovigilance platform to combat crop diseases, spore sampling, DNA diagnostics and predictive trajectory modelling were optimized. These tools revealed microbial dynamics and were validated by monitoring cereal rust fungal pathogens affecting wheat, oats, barley and rye across four growing seasons (2015-2018) in British Columbia and during the 2018 season in southern Alberta. ITS2 metabarcoding revealed disparity in aeromycobiota diversity and compositional structure across the Canadian Rocky Mountains, suggesting a barrier effect on air flow and pathogen dispersal. A novel bioinformatics classifier and curated cereal rust fungal ITS2 database, corroborated by real-time PCR, enhanced the precision of cereal rust fungal species identification. Random Forest modelling identified crop and land-use diversification as well as atmospheric pressure and moisture as key factors in rust distribution. As a valuable addition to explain observed differences and patterns in rust fungus distribution, trajectory HYSPLIT modelling tracked rust fungal urediniospores' northeastward dispersal from the Pacific Northwest towards southern British Columbia and Alberta, indicating multiple potential origins. Our Canadian case study exemplifies the power of an advanced biovigilance toolbox towards developing an early-warning system for farmers to detect and mitigate impending disease outbreaks.

Cytological and molecular characterization of wheat lines carrying leaf rust and stem rust resistance genes Lr24 and Sr24

Previous studies showed that Australian wheat cultivars Janz and Sunco carry leaf rust and stem rust resistance genes Lr24 and Sr24 derived from Thinopyrum ponticum chromosome arm 3AgL. However, the size of the alien segments carrying Lr24 and Sr24 in the lines were not determined. In this study, we used non-denaturing fluorescence in situ hybridization (ND-FISH), genomic in situ hybridization (GISH), and PCR-based landmark unique gene (PLUG) markers to visualize the alien segments in Janz and Sunco, and further compared them with the segments in US cultivars Agent and Amigo. The fraction length (FL) of the alien translocation in Agent was 0.70–1.00, whereas those in Janz, Sunco, and Amigo were smaller, at FL 0.85–1.00. It was deduced that the alien gene RAg encoding for red grain color and rust resistance genes Lr24 and Sr24 on chromosome arm 3AgL were in bins of FL 0.70–0.85 and 0.85–1.00, respectively. We retrieved and extracted nucleotide-binding site-leucine-rich repeat (NBS-LRR) receptor genes corresponding to the region of Lr24 and Sr24 on chromosomes 3E, and 3J, 3Js and 3St from the reference genome sequences of Th. elongatum and Th. intermedium, respectively. A set of molecular markers developed for Lr24 and Sr24 from those extracted NBS-LRR genes will provide valuable information for fine mapping and cloning of these genes.

Evaluation of some bread wheat varieties and monogenic lines for Adult Plant Resistance to Stem Rust and detection related proteins..

Evaluation of some bread wheat varieties and monogenic lines for Adult Plant Resistance to Stem Rust and detection related proteins..

Resurgence of wheat stem rust infections in western Europe: causes and how to curtail them.

Ten years ago, (black) stem rust - the most damaging of wheat (Triticum aestivum) rusts - re-emerged in western Europe. Disease incidences have since increased in scale and frequency. Here, we investigated the likely underlying causes and used those to propose urgently needed mitigating actions. We report that the first large-scale UK outbreak of the wheat stem rust fungus, Puccinia graminis f. sp. tritici (Pgt), in 2022 may have been caused by timely arrival of airborne urediniospores from southwest Europe. The drive towards later-maturing wheat varieties in the UK may be exacerbating Pgt incidences, which could have disastrous consequences. Indeed, infection assays showed that two UK Pgt isolates from 2022 could infect over 96% of current UK wheat varieties. We determined that the temperature response data in current disease risk simulation models are outdated. Analysis of germination rates for three current UK Pgt isolates showed substantial variation in temperature response functions, suggesting that the accuracy of disease risk simulations would be substantially enhanced by incorporating data from prevailing Pgt isolates. As Pgt incidences continue to accelerate in western Europe, we advocate for urgent action to curtail Pgt losses and help safeguard future wheat production across the region.

Sources of winter rye resistance to fungal diseases for phytoimmunity breeding

The work was carried out at the Federal Agrarian Scientific Center of the North-East in 2020–2022. More than 140 domestic varieties of winter rye were studied under conditions of Kirov region on provocative-infectious background of snow mold, powdery mildew, brown and stem rust, septoriosis, root rot, ergot. Commonly known methods were used to account for diseases. During the plant ontogenesis (from phase 31 to 85 on Zadoks scale), we analyzed the growth of fungal infection in the variety biocenoses. The nature of plant-microbe interactions and resistance parameters were evaluated according to two indicators PKRB (area under the disease development curve) and IS (resistance index). We identified 28 sortes characterized by nonspecific resistance to two or more diseases and slow (slow rusting) growth of infection in varietal biocenoses. Among them: Lika, Harmonia, Symphony, Perepel, Graphite, Graphite FP, Era, Eureka, Vikras, Amber, Chusovaya, Saratovskaya 7, etc. They can be used in breeding for phytoimmunity as sources. The highest yielding (840–1060 g/m2) among them are: Batiste, Dymka, Perepel, Lika, Symphony, Kiprez, Grafit FP, Flora, Eureka, Dana, Marusenka, Era, Saratovskaya 7, Chusovaya. The correlation coefficient (r) between the yield and regrowth after snow mold lesions varies from 0.49 (2022) to 0.87 (2020), which confirms the high harmfulness of this disease in the region. Rada, Kiprez, Flora, Lika, Batiste, Harmony, Symphony, Chusovaya can be of certain immunological value in breeding for ergot resistance, as they were much less affected by ergot than the standard and other varieties. The regression equations are linear (R2 = 0,96–0,99) and show a daily increase of brown rust (from 5,4 to 16,4 %) and stem rust (from 4,7 to 26,5 %).

Virulence phenotypes of Puccinia graminis on barley, wheat and oat in Canada from 2020 to 2022

Stem rust of barley and wheat is caused by the obligate pathogen Puccinia graminis f. sp. tritici (Pgt) and stem rust of oat is caused by P. graminis f. sp. avenae (Pga). Stem rust can be a very destructive disease of cereal crops and, until the development of resistant host varieties, was responsible for millions of dollars of losses to producers. Genetic host resistance is the most common and effective method to control stem rust on cereals. Knowledge of the virulence genes and races present in the pathogen population is important to identify effective host resistance genes for use by cereal plant breeders. The objectives of this study were to determine the incidence and severity of P. graminis in wheat, barley and oat in Manitoba, Canada, and assess the virulence frequencies and races of isolates collected from Manitoba, Saskatchewan and Ontario, Canada during 2020 to 2022. Stem rust incidence and severity was very light in Manitoba in 2020, 2021 and 2022. Virulence was not observed on resistance genes Sr30, Sr24 and Sr31 from Canadian collections of Pgt isolates made during 2020 to 2022. Race QFCSC was the most common race of Pgt in Canada, and races MCCFC and TPMKC were also common in Manitoba in 2022. Virulence to resistance genes Pg6, Pg10 and Pg16 was not observed among Pga isolates. The most common race of Pga from Manitoba and Saskatchewan was TGN, followed by SGB and TJS. The most frequent Pga races were TDJ, TDD and TGN in Ontario.

Characteristics of the spring common wheat variety ‘Balkysh’

One of the recent breeding work results of the FRC KazRC of RAS was the spring common wheat variety ‘Balkysh’, which was included in the State List of Breeding Achievements approved for use in the Middle Volga region in 2021. The purpose of the current study was to characterize the variety under the conditions of the last years of testing in comparison with other varieties. The study was carried out in the fields with gray forest soils of the Tatar RIA, located in the suburbs of Kazan, in 2019–2023. The variety ‘Balkysh’ is not inferior or superior in productivity and protein yield to the varieties most common in the Republic of Tatarstan; the mean productivity of the variety was 4.31 t/ha, protein yield was 0.54 t/ha. The variety is characterized with high productivity stability. The variety had 25 % of gluten in grain, 13.2 % of protein, 94 units of IDK. The peculiarity of the rheological dough properties of the variety ‘Balkysh’ was a low value of flour force with 109 u.a., 61 mm of dough elasticity, 121 u.ph. of dough dilution, which can be used to form grinding grain batches balanced in quality to reduce the load on dough mixing machines. The variety ‘Balkysh’ is characterized with high field complex resistance to major leaf and stem diseases, with not more than 5 % of damage caused with brown leaf and stem rust over the years of testing; powdery mildew resistance during epiphytoty years was not lower than 6 points (a lower one third of the plant was slightly affected). The variety ‘Balkysh’ is characterized as short-stemmed; the mean plant height was 65.7 cm, which is significantly lower than that of the varieties developed by the TatRIA.

AvrSr27 is a zinc-bound effector with a modular structure important for immune recognition.

Effector proteins are central to the success of plant pathogens, while immunity in host plants is driven by receptor-mediated recognition of these effectors. Understanding the molecular details of effector-receptor interactions is key for the engineering of novel immune receptors. Here, we experimentally determined the crystal structure of the Puccinia graminis f. sp. tritici (Pgt) effector AvrSr27, which was not accurately predicted using AlphaFold2. We characterised the role of the conserved cysteine residues in AvrSr27 using in vitro biochemical assays and examined Sr27-mediated recognition using transient expression in Nicotiana spp. and wheat protoplasts. The AvrSr27 structure contains a novel β-strand rich modular fold consisting of two structurally similar domains that bind to Zn2+ ions. The N-terminal domain of AvrSr27 is sufficient for interaction with Sr27 and triggering cell death. We identified two Pgt proteins structurally related to AvrSr27 but with low sequence identity that can also associate with Sr27, albeit more weakly. Though only the full-length proteins, trigger Sr27-dependent cell death in transient expression systems. Collectively, our findings have important implications for utilising protein prediction platforms for effector proteins, and those embarking on bespoke engineering of immunity receptors as solutions to plant disease.

First report of expansion of virulence in Puccinia striiformis f. sp. tritici to wheat resistance genes Yr10 and Yr24 in the Middle East.

Over the last decade, field assessments of the yellow rust differential lines for resistance genes Yr10 and Yr24 and race analysis in the Middle East have demonstrated efficient yellow rust control by Yr10 and Yr24 (=Yr26). Yellow rust samples collected during 2018-21 in Central West Asia & North and sub-Saharan Africa underwent race analysis at the Regional Cereal Rust Research Center in Izmir, Türkiye. The infected leaf segments were subjected to rehydration at 20°C for three hours. Subsequently, the leaf segments were rubbed on the first leaves of seedlings of susceptible cultivar Morocco. Inoculated seedlings were placed at 10°C in dark conditions with 95% humidity for 24 hrs, then moved to a growth chamber with a 16-hr light (220 µmolm-2s-1) cycle at 15°C and an eight-hour dark period at 12°C. Urediniospores were collected 15 days post-inoculation. A set of yellow rust differential lines including Morocco, Avocet 'S', Avocet 'R', Yr1/6* Avocet 'S', Kalyansona (Yr2), Vilmorin 23 (Yr3), Hybrid 46 (Yr4), Yr6/6* Avocet 'S', Yr7/6* Avocet 'S', Yr8/6* Avocet 'S', Yr9/6* Avocet 'S', Yr10/6* Avocet 'S', Moro (Yr10+), Yr17/6*Avocet 'S', Yr24/6* Avocet 'S', TP1295 (Yr25), Yr27/6* Avocet 'S', YrSp/6* Avocet 'S', Spalding Prolific (YrSP), Strubes Dickkopf (YrSD), Tres/6*Avocet'S', Cham 1, and Ambition was used in race analysis. A mixture of 2 mL Soltrol® and 0.5 mg fresh urediniospores was used to inoculate 10-day-old seedlings of the 23 differential varieties. Pre-inoculation, incubation, and post-inoculation conditions were the same as above. Seedling infection types (ITs) were recorded 15 days post-inoculation on a scale of 0 to 9 (McNeal et al. 1971), where ITs 0 to 6 are classified as low infection types (LITs= avirulent) and ITs 7 to 9 categorized as high infection types (HITs= virulent). HITs of 7 to 9 were observed for the first time on Yr10/6* Avocet 'S', Yr24/6* Avocet 'S', as well as on Moro (Yr10+) for 25 sample of the total 50 isolates from Lebanon and Türkiye in 2018. During the race analysis in 2019 to 2021, virulence for Yr10 and Yr24 was identified among tested samples from Egypt, Lebanon, Jordan, Syria, and Türkiye, indicating the expansion of virulence for Yr10 and Yr24 into new regions. HITs were observed for the durum wheat cultivar Cham 1 and wheat cultivar Ambition in all races. Virulence for YrA, Yr2, Yr6, Yr7, Yr8, Yr17, and 32 was common within the Yr10 and Yr24 virulent races, and virulence for YrSp and Yr27 were observed in low frequency. Molecular genotyping of 209 isolates, including the Yr10 virulent races, was performed using 19 microsatellite markers (Ali et al. 2017; Rodriguez-Algaba et al. 2017) and aligned with the Puccinia striiformis nomenclature system of the Global Rust Reference Center (GRRC). The results showed that 66 isolates were identical to the genotyping lineage "ME2018" identified in Egypt in 2018 by GRRC. This genetic lineage has now been designated as PstS17 (Hovmøller et al. 2023). The durum wheat cultivars have always been resistant to yellow rust in the Middle East. Seedling tests of 50 durum advanced lines from CIMMYT's International Durum Wheat Yield Nursery showed LITs in 45 accessions (90%) against an avirulent race for Yr10 and Yr24 (PstS2), but only 12% remained resistant while tested with a PstS17 (virulent for Yr10 and Yr24). This observation provides compelling evidence of the Yr10 and/or Yr24 presence within tested durum wheat germplasm. Continued monitoring of virulence and resistance of wheat germplasm to yellow rust is critical for successful breeding for rust resistance.

Registration of the “Woodies” multi–rust‐resistant barley germplasm

AbstractSelection for resistance to plant diseases is a continuous effort on the part of plant breeders. Sources of genetic resistance are often limited, despite considerable discovery efforts. Stem rust and stripe rust are two diseases of particular importance in barley (Hordeum vulgare L.) production. The present work aims to develop and deploy genotypes with resistance to these diseases that can be used in future breeding efforts. The Woodies, Woody‐1 (DH160733; Reg. no. GP‐218, PI 704479) and Woody‐2 (DH160754; Reg. no. GP‐219, PI 704480), are two doubled‐haploid genotypes produced via F1 anther culture named in honor of the late Lynn “Woody” Gallagher. These two‐row spring habit barley germplasm accessions were released by the Oregon Agricultural Experiment Station in 2023. These genotypes have demonstrated resistance to both stem and stripe rust at the seedling and adult plant stage in trials conducted between 2018 and 2023. The genetic basis of this resistance appears to be a novel quantitative trait locus conferring resistance to both diseases on chromosome 5H that is different from the known rpg4/Rpg5 complex for stem rust resistance found on the same chromosome. Seed can be requested from the Oregon State University Barley Breeding Program or from the NLGRP Germplasm repository.

Sudogda is a new variety of winter triticale for fodder production

Sudogda is a new variety of winter triticale for fodder production

Immunological structure and yield of winter rye varieties bred by the Federal Agricultural Research Center of the North-East named N. V. Rudnitsky

The study was carried out in the conditions of Kirov region in 2019–2023. Against provocative and infectious backgrounds of snow mold, root rot, ergot, powdery mildew, leaf and stem rust, the immunological state and yield of 15 varieties of winter rye created over a 73-year period were studied. Taking into account the breeding methods, the source material used and the year of creation, they were conditionally distributed over five successive periods of breeding and variety change: I – Vyatka 2, Kirovskaya 89; II – Falenskaya 4, Snezhana, Rushnik; III – Flora, Grafinya, Batist; IV – Lika, Talitsa; V – Symphoniya, Garmoniya, Graphit, Graphit FP, Perepel. When recording diseases, well-known methods were used. Research has shown that as a result of breeding, on artificial infectious backgrounds newly created varieties showed a decrease in the development of root rot (Flora, Perepel, Garmoniya – degree of damage 14.6, 15.5 and 15.0 %) and ergot (Flora, Grafinya, Batist, Lika, Symphoniya, Graphit FP, Garmoniya – damage 11.4...15.9 %), grain contamination with sclerotia – 0.38...1.84 %. In varieties of the I period of breeding the degree of root rot infection was 18.8 %, ergot infection – 31.7 %. There is no progress in breeding for resistance to powdery mildew and rust types. The most productive varieties are Lika and Batist (769.3 and 738.7 g/m2), which significantly exceed the Falenskaya 4 standard (578.8 g/m2). A close and significant dependence (p ≥ 095) was revealed between the yield of winter rye varieties and regrowth of plants after snow mold infection (r = 0.693...0.830) as well as grain contamination with sclerotia (r = -0.531...-0.712). The relationship between the yield of winter rye and the development of other studied diseases is insignificant and weak. Considering the high harmfulness of snow mold and ergot in the research region, it is necessary to continue to carry out breeding improvement of varieties for these characteristics, as well as to increase resistance to powdery mildew and types of rust.

Selection based on the phenomenic approach and agronomic ideotic of white oat

AbstractThis work aimed to propose multivariate selection strategies reconciling the agronomic ideotype and vegetation indices to obtain genotypes with high tillering, early cycle, tolerant to lodging, and foliar diseases. The sowing of white oat lines was carried out on April 27, 2023, allocated in an experimental design of blocks augmented with interspersed controls. The regular treatments correspond to 593 lines of white oat and the common treatments were represented by the cultivars URS Olada, URS Altaneira, and IPR Artêmis arranged in four replications. The measurements of variables of agronomic interest took place in each experimental unit as follows: percentage of tillering, days to flowering, percentage of lodging, percentage of leaf rust, percentage of stem rust, and percentage of leaf spots. The phenomic analyses took place through flights carried out with a specialized drone, equipped with a 20 MP resolution camera and standard height (80 m). The best proposed indices were index for reducing the percentage of lodging with normalized green (NG), green–red ratio (IGR), soil color index (SCI), green leaf index (GLI), visible atmospheric resistant index (VARI), green leaf index 2 (GLI2), red–blue (RB), blue green pigment (BGI), normalized red–blue difference index (NRBDI), green–blue ratio, BIM, normalized green–blue difference index (NGBDI), and ExGR; index for reducing days to flowering with brightness index (BI), NRBDI, days to flowering (DF), gray (GRAY), IGR, average intensity (L), normalized red (NR), RGRI, SCI, BGI, BIM, GLI, NGBDI, and NG; and index for reducing the percentage of stem rust with NG, BI, Gray2, GLI2, RGRI, GLI, VARI, BGI, L, NR, RB, and coloration index. Only two lines were selected concomitantly with multivariate indices, line L167 (M5, SA) and L426 (M6, ETMS), that combine lodging tolerance and leaf rust genes.

Physio-Biochemical, Anatomical, and Molecular Analysis of Resistant and Susceptible Wheat Cultivars Infected with TTKSK, TTKST, and TTTSK Novel Puccinia graminis Races.

Stem rust, caused by Puccinia graminis f.sp. tritici, is one of the most dangerous rust diseases on wheat. Through physiological, biochemical, and molecular analysis, the relationship between the change in resistance of 15 wheat cultivars to stem rust disease and the response of 41 stem rust resistance genes (Sr,s) as well as TTKSK, TTKST, and TTTSK races was explained. Some cultivars and Sr genes, such as Gemmeiza-9, Gemmeiza-11, Sids-13, Sakha-94, Misr-1, Misr-2, Sr31, and Sr38, became susceptible to infection. Other new cultivars include Mir-3 and Sakha-95, and Sr genes 13, 37, 40, GT, and FR*2/SRTT3-SRTT3-SR10 remain resistant. Some resistance genes have been identified in these resistant cultivars: Sr2, Sr13, Sr24, Sr36, and Sr40. Sr31 was not detected in any cultivars. Reactive oxygen species such as hydrogen peroxide and superoxide, enzymes activities (catalase, peroxidase, and polyphenoloxidase), and electrolyte leakage were increased in the highly susceptible cultivars, while they decreased in the resistant ones. Anatomical characteristics such as the thickness of the epidermis, ground tissue, phloem tissue and vascular bundle diameter in the midrib were decreased in susceptible cultivars compared with resistant cultivars. Our results indicated that some races (TTKSK, TTKST, and TTTSK) appeared for the first time in Egypt and many other countries, which broke the resistant cultivars. The wheat rust breeding program must rely on land races and pyramiding genes in order to develop new resistance genes that will survive for a very long time.

Phylogenesis of virulent races of Puccinia graminis f. sp. tritici based on phenotyping and genotyping using newly developed SNP markers for genetic groups in clades

Ug99 (TTKSK) and Digalu (TKTTF) race groups of Puccinia graminis f. sp. tritici (Pgt), are thought to be the most virulent, rendering many wheat stem rust resistance genes (Sr) ineffective. A total of 600 single pustule Pgt isolates were collected from eight Egyptian provinces during 2016–2022, undergoing both phenotyping and genotyping assays. Among these, 129 viable samples (v-samples) underwent phenotyping using the North American differentials delineated to Pgt races in the TTKS (Ug99) and TKTTF race groups, identifying 24 distinct physiologic races of Pgt. Notably, seven virulent races, TKTTF (Digalu), TKKTF, TKPTF, TKKTP, TTRTF, TTTTF, and TKFTF, were discovered in Egypt. The host reaction of wheat germplasm to these seven races indicated a high level of susceptibility. A set of 437 dead samples (d-samples) of Pgt isolates from Egypt were genotyped using newly created 17 core SNP markers. Genotypic analysis revealed that these seven races could be classified into two major clades: III and IV. Within these clades, six subclades were identified, namely III-B, IV-A.2, IV-B, IV-E.1, IV-E.2, and IV-F. These SNP genotypes exhibited a broad geographic distribution, highlighting the global movement of Pgt populations across Europe, Asia, and Africa. Notably, none of these genetic groups were present in Egypt before 2016. The most prevalent genotypes were subclades IV-A.2 (TKTTF; Digalu), IV-E.2 (TKKTF, TKPTF, TKFTF), and III-B (TTRTF). The prevalence of these unique genotypes/races suggests clonal reproduction and evolution within them. Race TKKTP (subclade IV-E.1) is particularly concerning because of its ability to overcome the resistance conferred by gene Sr24 against race TTKSK (Ug99). Phylogenetic analysis of Pgt genetic groups revealed that the majority of identified races belong to TKTTF (Digalu) race group (subclade IV-A.2). Notably, no races were found to belong to the TTKS (Ug99) race group (clade I). This information should help breeders select a broader range of resistance genes that are both diverse and effective to enhance the durability of stem rust resistance.